2017-09-07 LeetCode_002 Add Two Numbers

2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Solution：

/**

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* Definition for singly-linked list.

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* struct ListNode {

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*     int val;

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*     ListNode *next;

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*     ListNode(int x) : val(x), next(NULL) {}

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* };

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*/

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class Solution {

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public:

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   ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {

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       ListNode *l3 = new ListNode(l1->val+l2->val), *p = l3;

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       l1 = l1->next; l2 = l2->next;

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       for (; l1 != NULL || l2 != NULL; l1 = (l1 == NULL ? NULL : l1->next), l2 = (l2 == NULL ? NULL : l2->next)) {

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           int a = 0, b = 0;

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           if (l1 != NULL) a = l1->val;

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           if (l2 != NULL) b = l2->val;

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           p->next = new ListNode(a+b+p->val/10);

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           p->val %= 10;

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           p = p->next;

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}

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if (p->val >= 10) {

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p->next = new ListNode(p->val/10);

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           p->val %= 10;

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}

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return l3;

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   }

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};